Produced water is a term used in the oil industry to describe water that is produced along with the desired oil and gas during the extraction process. Oil and gas reservoirs have a natural water layer (formation water) that lies under the hydrocarbons. Oil reservoirs frequently contain large volumes of water, and gas reservoirs tend to have smaller quantities of water. To achieve maximum oil recovery, additional water is injected into the reservoirs to help force the oil to the surface. Both the formation water and injected water are eventually produced along with the oil; the resulting water is called produced water. As oil and gas fields become depleted, the produced water content of the oil increases.
The combination of the formation water and injected water that is recovered during the oil and gas extraction process creates a surplus of produced water above and beyond that needed for continued oil extraction. That surplus of produced water is an industrial waste and must be properly treated and disposed.
Historically, produced water was disposed of in large evaporation ponds. However, this has become an increasingly unacceptable disposal method from both environmental and social perspectives. Produced water is considered an industrial waste and producers are required to treat and employ beneficial re-uses for produced water. Re-uses for produced water include direct injection, direct-use of untreated water, and discharge to surface waters. Both direct injection and discharge to surface waters requires the produced water to be treated to meet U.S. Environmental Protection Agency (EPA) standards, and is regulated by state governments under the Safe Drinking Water Act. However, to achieve these levels of water treatment, typically the oil and gas production industry lacks the capabilities at the satellite oil and gas well sites to properly treat the produced water to the EPA and Safe Drinking Water Act standards. This lack of capability at the satellite oil and gas well sites requires the shipment of the produced water to facilities capable of treating the produced water to the applicable EPA and Safe Drinking Water Act standards. Treating produced water creates a significant cost to the oil and gas industry.